Axial turbo-machine assembly with multiple guide vane ring sectors and a method of mounting thereof

ABSTRACT

The invention relates to a method and a device for mounting an axial turbo-machine, preferably a low-pressure compressor for a gas turbine, constructed without a parting line with a whole or constructed rotor. From the design point of view, problems arise regarding the mounting of the stationary guide vane rings in the case of a design without a parting line and a whole rotor. The problem is solved by dividing the guide vane rings into sectors in a number greater than two. These sectors are brought radially into position and are guided and fixed in the correct position by guide rings which are applied around each guide vane ring composed from sectors. Each composed guide vane ring with the surrounding guide ring is guided and fixed to the preceding guide ring and all the guide vane rings are successively built up around the whole or constructed rotor. The guide rings mounted together constitute a stiff annular element.

TECHNICAL FIELD

The invention relates to axial turbo-machines, preferably low-pressurecompressors for gas turbines and to a method and a device for mountingof a machine concept without a parting line and with a non-divisiblerotor.

BACKGROUND OF THE INVENTION

When designing axial turbo-machines comprising a bladed rotor in severalstages and partitions comprising stationary guide vanes, an axialparting line is preferably chosen. The housing of the turbo-machine isthus given a top half and a bottom half, which are bolted together inthe parting line by means of flanges. The partitions, which contain thestationary guide vanes, are divided into two halves, one half beingplaced in the bottom half of the housing where it is aligned andcentered by means arranged between the wall half and the housing. Thebladed rotor is placed in its bearing positions in the ends of thebottom half, the rotor discs then being situated between the mountedpartitions of the bottom half. The other partition halves are mounted inthe top half of the housing,

The principle described above is the most frequently used. However,depending on the type of turbo-machine, it is a question of partitionsin the form of plates with a relatively low (a small radial extent)guide vane channel to the extreme case involving guide vane latticesattached to the inside of the housing without any wall construction.Action type steam turbines have marked partitions whereas guide vanelattices for a gas turbine compressor can only comprise guide vanesattached to the inner walls of the compressor housing with or withoutany connecting element at the inner limit of the guide vanes nearest therotor shaft.

The parting line entails an accumulation of material and a departurefrom the rotational symmetry, which is a drawback upon start-up and loadchanges. Uneven temperature heating arises, which above all causesovalities. To prevent this from giving rise to cutting betweenstationary parts and parts of the rotating rotor, enlarged clearances inthe flow channel are required, which causes major leakage and inferiorperformance of the machine. The negative effect of parting lines isminimized either by minimizing the amount of material in the partingline by constructing in high-strength material with thin thicknesses(gas turbines for aircraft) or choosing to change the load of theturbine slowly (large steam turbines for high pressures and casthousings).

Parting lines are sensitive to leakage, which means that the necessarystiffness requires a certain amount of material in the flanges.Consequently, there is a reason for designing turbo-machinery completelyrotationally symmetrically without parting lines. From the design pointof view the problem then arises how to proceed to mount the stationarylattices between the rotor stages. One known turbine concept compriseshigh-pressure turbines which are of the so-called barrel type, that is,they have no parting lines. Such a turbine is composed of an innerhousing, composed of axially mounted rings screwed together, which fixthe partitions which in turn are divided into two halves and insertedradially into their positions and locked there by the above-mentionedrings. The ring package is guided by guiding elements in the surroundingcast turbine housing.

When designing an axial turbo-machine, preferably a gas turbine, it isadvantageous also to avoid parting lines to obtain a rotationallysymmetrical design.

Constructively, the mounting problem has been solved by using builtrotors, which when mounting the machine are built up step-by-stepsuccessively with whole guide vane rings sandwiched in between (in theabove steam turbine application referred to as partitions). This methodis technically applicable.

However, it would entail technical and economic advantages if it werepossible to use non-divisible rotors while at the same time utilizing adesign without a parting line.

For axial turbo-machines, preferably high-pressure compressors for gasturbines, this is possible since it is possible to mount the guide vanerings guide vane by guide vane in the housing, the boundary of the guidevane nearest the rotor shaft being free and without any structuralmember which interconnects the guide vane tips. The limitation that thisdesign entails has to do with oscillations and is dealt with by theguide vanes being short as compared with their chord.

With regard to an axial turbo-machine, preferably a low-pressurecompressor for a gas turbine, the guide vanes are of such a length thatthe free attachment mentioned above creates problems from the point ofview of oscillation. A constructive design could be guide vanes withlarge chords, which, however, entails a longer machine. In the case ofnon-constant speed machines, the oscillation problems in blade and guidevane lattices are difficult to overcome and require accuratecalculations and advanced design solutions. Design solutions with gooddamping properties are desired.

SUMMARY OF THE INVENTION

An axial turbo-machine, preferably a low-pressure compressor for a gasturbine, is constructed without parting lines and the rotor 24 ismounted together with the static components in undivided state. Theguide vane rings are divided into sectors 9 of a number greater thantwo. The sectors are inserted radially into their correct position. Bymeans of axial guide pins 12 or other fixing elements, the sectors arefixed in the correct angular position in the plane perpendicularly tothe direction of the rotor shaft. Between the sectors, space is providedfor the thermal expansion of the sectors.

Axially and radially the sectors are fixed by whole guide rings (e.g.13, 14), which are mounted axially in relation to each other, fixed viaaxial bolts or other types of fixing elements and guided towards eachother radially by means of guide surfaces (e.g. 15, 26) or some otherguiding principle, for example by axial pins. The amount of material inthe guide rings is adapted such that the heating rate and the thermalexpansion thus obtained follow the corresponding heating and thermalexpansion of the rotor upon start-up and load changes.

Since the guide rings constitute a stiff structural member, the fasterheating of the sectors following a load change, and the thermalexpansion thus obtained, will not give rise to the sectors expandingradially outwards, but they will make use of the above-mentioned gapsbetween the sectors and will expand inwards towards the rotor shaft. Thelimiting surface towards the rotor shaft, commonly formed by thesectors, exhibits small deviations from the circular shape, whichappears in a uniformly heated machine.

The sectors, the outer and inner boundaries of which consist ofinterconnecting elements 6, 7, create oscillation-damping units and, inaddition, at the attachment of the guide vanes to the interconnectingelements, damping material can be enclosed to further improve thedamping ability of the sectors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sectional view of an axial low-pressure compressor for agas turbine with an air inlet at 1, a flow channel at 2 and an outlet at3. The center line of the rotor shaft is designated 4. The rotor 24 is,according to the figure, constructed from individual units which arebolted together to form a rotor body. According to the invention, therotor may be made in one piece.

FIG. 2 shows an enlarged part of the flow channel in FIG. 1 (dash-dottedsquare). The figure shows a design example with such an embodiment thatthe inventive concept can be applied.

FIG. 3 shows a sector of guide vanes with outer and innerinterconnecting structural members.

FIG. 4 shows the sector according to FIG. 3, seen axially in thedirection of the arrow 25. The sector shown comprises five guide vanes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

After manufacture, guide vanes 5 and attachment elements 6, 7 at boththeir ends constitute a whole in the form of an annular structuralmember. This is referred to as a guide vane ring. This ring is dividedby means of radial sections into a number of sectors 9, the number beinggreater than two. FIGS. 3 and 4 show such a sector in two views. In thisexample the sector comprises five guide vanes 5a-5e, held together by anouter structural member 6 and an inner structural member 7. Thestructural members 6, 7 enclose a damping material 8.

FIG. 2 shows a sector 9 of a guide vane ring in a position A, from whichposition A the sector 9 is inserted radially according to the arrow 10into a position B. The insertion also comprises an axial displacementinto a guide means 11 and over a guide pin 12. The guide pin 12 fixesthe sector in the correct angular position in the plane perpendicular tothe direction of the rotor shaft. The guide means 11 fixes the sectorradially. The guide vane sector 9 is fixed radially by the guide means11 in the guide ring 13. After all the sectors of the guide vane ringhave been fixed in relation to the guide ring 13, the guide ring 14 ismoved axially in the direction of the arrow C in over the mountedsectors, is guided against the guide surfaces 15, 16 and pressed againstthe guide ring 13. Thereby, the sectors 9 are now fixed radially in thetwo guide surfaces 29 and 16 of the structural outer member 6 in theguide surface 11 of the guide ring 13 and the guide surface 27 of theguide ring 14. The guide ring 14 is guided with its guide surface 26against the guide surface 15 on the guide ring 13 and is thus radiallyguided against the preceding guide ring, here guide ring 13. With guidering 14 axially in contact with guide ring 13, the sectors 9 are axiallyfixed. With guide ring 14 in mounted position, the mounting of thesectors included in the next guide vane ring is started, which isperformed in the same way as described above.

The guide rings included in the compressor are bolted together axiallyin groups of rings or individually, which fixes the guide rings axially.This is clear from FIG. 1, in which the bolted joint 17 interconnectsthree guide rings whereas the bolted joint 18 only fixes the succeedingguide ring to the preceding one. FIG. 2 shows a bolted joint 19 whichinterconnects guide rings 13, 20, 21 and further ring elements (notshown). Numeral 22 designates a blade mounted on the rotor disc 23.Numeral 24 designates the center line of the rotor.

I claim:
 1. A method of mounting an axial turbo-machine assembly in agas turbine constructed with a housing without a parting line, saidmethod comprising the steps of:forming a plurality of radial sectors,each said sector including a plurality of vanes; bringing at least threesaid sectors radially into a position to form a vane ring which enclosesa rotor of said assembly; and applying a guide ring around an outersurface of said vane ring for fixing each said sector in said position.2. A method according to claim 1, further comprising fixing said guidering axially by at least one fastener.
 3. A method according to claim 1,further comprisingdisplacing said sectors axially towards a previouslymounted vane ring after each said sector is radially brought into saidposition, and fixing each said sector radially in said previouslymounted vane ring by at least one guide.
 4. A method according to claim3, wherein said fixing includes fixing angularly each said sector in aplane perpendicular to the direction of a rotor shaft which is arotational center of said assembly.
 5. A method according to claim 1,wherein said applying step includes fixing each said sector axially bysaid guide ring.
 6. A method according to claim 1, further comprisingproviding guide surfaces in said guide ring and in said sectors, andfitting at least one guide surface of said guide ring with at least oneguide surface of said sectors for fixing said sectors radially.
 7. Anaxial turbo-machine assembly in a gas turbine, comprising:a multiple ofvane rings for enclosing a rotor of said assembly, wherein each saidvane ring is formed by at least three radial sectors spaced apart fromeach other, each said sector comprising at least two vanes and expandingindependently of the remaining sectors of said vane ring in a radialinward direction due to heat in said gas turbine; and a guide ringapplied around an outer surface of each vane ring for radially andaxially fixing each said sector in a proper position in said assembly.8. An assembly according to claim 7, further comprising fastening meansfor axially fixing each said sector in said proper position.
 9. Anassembly according to claim 7, wherein said sectors are axiallydisplaceable towards a previously mounted vane ring after each saidsector is radially brought into said position to form said vane ring,and further comprising at least one guide for radially fixing saidsectors in said previously mounted vane ring.
 10. An assembly accordingto claim 9, wherein each said sector is fixed angularly in a planeperpendicular to the direction of a rotor shaft which is a rotationalcenter of said assembly.
 11. An assembly according to claim 7, whereineach said sector is axially fixed by said guide ring.
 12. An assemblyaccording to claim 7, further comprising guide surfaces located in saidguide ring and in said sectors, wherein at least one said guide surfaceof said guide ring is fitted with at least one guide surface of saidsector for fixing said sector radially.
 13. An axial turbo-machineassembly in a gas turbine, comprising:a plurality of vanes divided intoat least three radial sectors which form a vane ring, wherein each saidsector comprises a plurality of said vanes and expands independently ofthe remaining sectors of said vane ring in a radial inward direction dueto heat in said gas turbine; and a guide ring applied around an outersurface of said vane ring for fixing said sectors in a proper positionin said assembly.